Olefin disproportionation catalyst

ABSTRACT

An improved olefin disproportionation catalyst produced by contacting an inorganic refractory oxide containing a catalytic amount of molybdenum oxide with a promoting amount of elemental metals of the group consisting of tin and magnesium.

This application is a divisional of U.S. Ser. No. 207,565, filed Nov.17, 1980.

This invention relates to the disproportionation of olefins. In anotheraspect this invention relates to a disproportionation catalyst. In stillanother aspect, this invention relates to a novel method for producing adisproportionation reaction.

The disproportionation, or metathesis, of olefins is a reaction in whichone or more olefinic compounds are transformed into other olefins ofdifferent molecular weights. The disproportionation of an olefin toproduce one olefin of a higher molecular weight and one olefin of alower molecular weight can also be referred to asself-disproportionation. For example, propene can be disproportionatedto ethylene and cis- and trans-2-butene. Another type ofdisproportionation involves the codisproportionation of two differentolefins to form still other olefins. An example would be the reaction ofone molecule of 2-butene with one molecule of 3-hexene to produce twomolecules of 2-pentene.

The term "disproportionation reaction" as used herein is intended toinclude all variations of disproportionation reactions including:

(1) The disproportionation of an acyclic mono- or polyene having atleast three carbon atoms into other mono- or polyenes of both higher andlower number of carbon atoms; for example, the disproportionation ofpropylene yields ethylene and butenes; the disproportionation of1,5-hexadiene yields ethylene and 1,5,9-decatriene;

(2) The conversion of an acyclic mono- or polyene having three or morecarbon atoms and a different acyclic mono- or polyene having three ormore carbon atoms to produce different acyclic olefins; for example, theconversion of propylene and isobutylene yields ethylene and isopentene;

(3) The conversion of ethylene and an internal acyclic mono- or polyenehaving four or more carbon atoms to produce other olefins having a lowernumber of carbon atoms than that of the acyclic mono- or polyenes; forexample, the conversion of ethylene plus 4-methylpentene-2 yields3-methylbutene-1 and propylene;

(4) The conversion of ethylene or an acyclic mono- or polyene havingthree or more carbon atoms with a cyclic mono- or cyclic polyene toproduce an acyclic polyene having a higher number of carbon atoms thanthat of any of the starting materials; for example, the conversion ofcyclohexene and 2-butene yields 2,8-decadiene; the conversion of1,5-cyclooctadiene and ethylene yields 1,5,9-decatriene;

(5) The conversion of one or more cyclic mono- or cyclic polyenes toproduce a cyclic polyene having a higher number of carbon atoms than anyof the starting materials; for example, the conversion of cycloocteneyields cyclohexadiene;

(6) The conversion of an acyclic polyene having at least 7 carbon atomsand having at least 5 carbon atoms between any two double bonds toproduce acyclic and cyclic mono- and polyenes having a lower number ofcarbon atoms than that of the feed; for example, the conversion of1,7-octadiene yields cyclohexene and ethylene; or

(7) The conversion of one or more acyclic polyenes having at least threecarbon atoms between any two double bonds to produce acyclic and cyclicmono- and polyenes generally having both a higher and lower number ofcarbon atoms than that of the feed material; for example, the conversionof 1,4-pentadiene yields 1,4-cyclohexadiene and ethylene.

Among the catalysts that have been developed for disproportionation arethose comprising inorganic refractory oxides containing a catalyticamount of molybdenum oxide. The present invention is based upon thediscovery of a way to improve the activity of such a catalyst.

SUMMARY OF INVENTION

In accordance with the present invention, a disproportionation catalystcomprising inorganic refractory oxide containing a catalytic amount ofmolybdenum oxide is improved by contacting said catalyst with apromoting amount of at least one elemental metal selected from the groupconsisting of barium and magnesium under conditions suitable for saidmetal to promote the activity said molybdenum oxide. In a preferredembodiment elemental tin is employed in combination with magnesium.

DESCRIPTION OF PREFERRED EMBODIMENTS

The inorganic refractory oxide comprises solid inorganic oxide supportcontaining a major proportion of alumina or silica. Such materials arecommonly known as refractory oxides and include, for example, silica,alumina, magnesia-alumina, silica-alumina, titania-alumina,zirconia-alumina, and alumina-titania-zirconia. Preferred refractorymetal oxides are alumina or silica refractory oxides, especially highpurity forms such as those containing at least 99 percent of alumina orsilica. Generally, the refractory oxide has a surface area of at least25 m² /g and preferably the surface area is from about 100 m² /g.

Molybdenum oxide can be combined with the refractory oxide support inany conventional manner such as dry mixing, impregnation from a diluent,ion exchange, or the like. The oxides can be added directly or in theform of molybdenum compounds that can be converted to oxides bycalcination. The calcination is conducted by heating the impregnatedrefractory oxide in the presence of a nonreducing gas, such as nitrogen,argon, carbon monoxide, or oxygen-containing gas such as air, underconditions sufficient to convert the molybdenum compound to the oxide.Temperatures in the range of about 350° C. to about 800° C. aregenerally satisfactory for such calcination.

The proportion of the molybdenum oxide combined with the refractoryoxide can be varied, but generally the refractory oxide will contain atleast 0.1 percent by weight of molybdenum oxide, with amounts from about0.2 to 50 percent by weight being preferred, and 1 to 15 percentespecially preferred, said weight percent being based upon the combinedweights of the refractory oxide and the molybdenum oxide.

The molybdenum oxide catalyst is then combined with a promoting amountof an elemental metal selected from magnesium and barium. The amount ofpromoting metal employed can vary depending upon the level of activationdesired. Generally the elemental metal will be employed in an amount inthe range of about 0.5 to about 20, preferably about 2 to about 10weight percent based on the weight of the molybdenum oxide catalystprior to the addition of the elemental metal. In the preferredembodiment in which elemental tin is employed in combination withmagnesium, the elemental tin is employed in an amount in the range ofabout 1 to about 10, preferably about 2 to about 5 weight percent basedon the weight of the molybdenum oxide catalyst prior to the addition ofthe elemental metals.

The elemental metal can be combined with the catalyst in any suitablemanner. The metal in a powdered form can be admixed with the catalyst ormore preferably the metal is applied to the catalyst in a molten orvaporous form. This can be accomplished, for instance, by melting themetal and dropping the molten metal on the catalyst or by passing astream of inert gas such as nitrogen or argon through the molten metaland then over the catalyst.

It is essential that the combination of the elemental metal and thecatalyst be heated to an elevated temperature sufficient to cause thepromotion to take place. Generally, this involves heating the catalystto at least the melting temperature of the elemental metal. The lengthof time heating the catalyst composite is generally in the range ofabout 1 minute to about 10 hours, preferably on the order of about 10minutes to about 30 minutes. It is accordingly currently preferred toapply the metal to a bed of the catalyst and then flow a suitable gas,such as nitrogen, through the bed at the melting temperature of themetal for a length of time sufficient to obtain a substantialdistribution of the metal in the catalyst. The resulting catalyst isthen immediately suitable for use in the disproportionation reaction.Generally the temperature and time required can be determined byobserving the catalyst while it is being heated. Generally, there willbe an obvious color change in the catalyst which can be used as anindicator that the catalyst is ready for use.

An oxidizing atmosphere has been found to have an adverse effect uponthe promoting effect of the elemental metals. Accordingly, it isdesirable to protect the promoted catalyst from oxidizing atmosphereparticularly while the catalyst is at temperatures greater than aboutnormal room temperature. This can be done by keeping the promotedcatalyst under a nondeleterious atmosphere, such as nitrogen, until use.

The promoted catalyst can be used in disproportionation reactions in aconventional manner. The reaction temperature can vary depending uponthe type of refractory oxide employed. Typically, the disproportionationis carried out at a temperature in the range of about 100° to about 600°C., preferably about 200° to about 500° C. Generally, a temperature inthe range of about 100° to 300° C. is preferred when an alumina supportis employed and a temperature in the range of 200° to 500° C. preferredwhen a silica support is employed.

The disproportionation reaction can be carried out by contacting theolefins to be disproportionated with the catalyst in the liquid phase orthe gas phase, depending on structure and molecular weight of theolefins, temperature and pressure.

The pressure during the disproportionation reaction may vary betweenwide limits. Pressures between 0.1 and 500 atm. are suitable; preferredpressures are between 1 and 40 atm.

If the reaction is carried out in the liquid phase, solvents or diluentsfor the reactants may be used. Aliphatic saturated hydrocarbons (e.g.pentane, hexane, cyclohexane, dodecane) and aromatic hydrocarbons suchas benzene and toluene are suitable. If the reaction is carried out inthe gaseous phase, diluents such as aliphatic hydrocarbons (e.g.methane, ethane, and/or substantially inert gases (e.g., nitrogen,carbon dioxide) may be present. Preferably the disproportionationreaction is effected in the absence of dry significant amounts ofdeactivating materials such as water and oxygen.

The length of time during which the olefinically unsaturated compoundsto be disproportionated are contacted with the catalyst is not verycritical, and may conveniently vary between 0.1 seconds and 24 hours,although longer and shorter contact times may be used. The contact timeneeded to obtain a reasonable yield of disproportionated productsdepends on several factors such as the activity of the catalyst,temperature, pressure and structure of the olefinically unsaturatedcompounds to be disproportionated.

The process of the invention can be effected batchwise or continuously,with fixed catalyst beds, slurried catalysts, fluidized beds or by usingany other conventional contacting techniques. The soliddisproportionation catalysts are applied in any appropriate form, forexample, as powders, flakes, pellets, spheres or extrudates.

THE PRODUCTS

According to the process of the invention two olefinic reactants aredisproportionated to a product comprising olefin(s) having a totalnumber of carbon atoms equal to the sum of the carbon atoms of the twoolefinic reactants and having a number of ethylenic linkages equal tothe sum of the ethylenic double bonds of the reactants.

One variation of the process comprises the disproportionation of twomolecules of the same olefinic reactant. The reaction of two moleculesof an acyclic olefin of Formula I generally produces one olefin of ahigher carbon number and one olefin of a lower carbon number as depictedin equation (1) ##STR1## wherein R and R' have the previously statedsignificance. If R and R' represent identical groups, it is appreciatedthat the disproportionation reaction will not cause any skeletal changesas the products RCH═CHR and R'CH═CHR' will be equivalent to R'CH═CHR. Byway of specific illustration, the reaction of two molecules of propyleneproduces ethylene and 2-butene. However, the reaction of two moleculesof 2-butene produces two molecules of 2-butene. The reaction of twomolecules of cyclic olefinic reactant of Formula II, however, generallyproduces a cyclic olefin produced as depicted in equation (2) ##STR2##By way of specific illustration, the reaction of two molecules ofcyclooctene produces 1,9-cyclohexadecadiene.

Another variation of the process comprises the disproportionation of twodifferent acyclic olefinic reactants. By way of specific illustration,the reaction of 2-butene and 3-hexene produces two molecules of2-pentene and the reaction of 2-butene with 1,4-polybutadiene producestwo molecules of polybutadiene having a molecular weight which is lessthan the molecular weight of the starting 1,4-polybutadiene.

Still another variation of the process is "ring-opening"disproportionation wherein an acyclic olefinic reactant represented byFormula I is contacted with a cyclic olefinic reactant represented byFormula II. The product of "ring-opening" is a single olefinic compoundwith one less carbocyclic ring than the cyclic olefinic reactant ofFormula II. In terms of the Formulas I and II, the product isrepresented by Formula III. ##STR3## wherein R, R' and A have previouslystated significance. By way of specific illustration, from reaction of2-butene and cyclopentene is produced 2,7-nonadiene. Other typicaldisproportionation products include 2,8-decadiene produced by reactionof cyclohexene and 2-butene, 3,8-undecadiene produced from 3-hexene andcyclopentene, 1,5,9-decatriene produced by reaction of ethylene and1,5-cyclooctadiene, and 1,4-divinylcyclohexane from ethylene andbicyclo(2.2.2)oct-2-ene.

In "ring-opening" disproportionation, the cyclic olefinic reactant ispreferably a monocyclic or a bicyclic olefinic reactant of up to twoethylenic linkages and most preferably is a monocyclic, monoolefinicreactant of from five to eight carbon atoms, and the acyclic olefinicreactant is preferably an internal olefin which is symmetrical about thedouble bond, i.e., those olefins wherein both R and R' groups are alkyland R═R'. The molar ratio of cyclic olefinic reactant to the acyclicolefin in ring-opening disproportionation is not critical, although itis frequently useful to employ a molar excess of the acyclic olefin.Molar ratios of acyclic olefin to cyclic olefin reactant from about 1:1to about 20:1 are satisfactory with molar ratios from about 1:1 to about10:1 being preferred.

It is appreciated that an olefinic product produced by any variation ofthe disproportionation process can undergo further disproportionationwith another olefin present in the reaction mixture. For example,1,6-heptadiene produced from reaction of cyclopentene and ethylene canreact with another molecule of cyclopentene to produce1,6,11-dodecatriene, and 1,9-cyclohexadecadiene produced from reactionof two molecules of cyclooctene can react with additional molecules ofcyclooctene to give a high molecular weight monocyclic polyene.

The olefinic products, for the most part, have established utility asprecursors of polymers, e.g., as the third component ofethylene-propylene terpolymers useful as synthetic elastomers. Cleavageof the ethylenic bonds of polyolefinic products as by ozonizationproduces di- or polycarboxylic acids which are reacted with diamines,e.g., hexamethylenediamine, to form Nylons which are useful in syntheticfibers. The olefinic products are converted to secondary and tertiaryalcohols as by sulfuric acid-catalyzed hydration. Alternatively, theolefinic products are converted by conventional "Oxo" processes toaldehydes which are hydrogenated with conventional catalysts to thecorresponding alcohols. The C₁₂ -C₂₀ alcohols thereby produced areethoxylated as by reaction with ethylene oxide in the presence of abasic catalyst, e.g., sodium hydroxide, to form conventional detergentsand the lower molecular weight alcohols are esterified by reaction withpolybasic acids, e.g., phthalic acid, to form plasticizers for polyvinylchloride.

A further understanding of the present invention and its advantages willbe provided by reference to the following examples.

EXAMPLE I

A series of runs were made to determine the effect of temperature ondisproportionation of propylene over a silica supported molybdenum oxidecatalyst containing about 8 weight percent molybdenum oxide.

In the first run the catalyst was placed in a tubular disproportionationcatalyst and calcined at about 550° C. for about 1 hour with flowingair, then flushed with nitrogen and cooled to about 460° C. Then drysubstantially pure propylene was passed through the catalyst bed. Thereaction temperature was maintained at about 460° C. and samples of thereactor effluent analyzed at given time periods by GLC to determine thepercent conversion of propylene. The flow rate of the propylene wasabout 108 cc/minute.

After this run the catalyst was subjected to calcination in flowing airat 550° C. for about 30 minutes, again flushed with nitrogen and thenused for disproportionation of the propylene but this time at 418° C.The flow rate for propylene was about 106 cc/minute.

After this run the catalyst was again subjected to calcination this timeat 560° C. for 30 minutes, flushed with nitrogen and then used fordisproportionation of the propylene at about 356° C. and a flow rateabout 103 cc/minute.

The results of those three runs are summarized in Table I.

                  TABLE I                                                         ______________________________________                                        % Propylene Conversion                                                                     Time                                                             Reaction Temperature                                                                         15      30    45     60  90                                    ______________________________________                                        460° C. 20      21    21     21  *                                     418° C. 15      18    18     18  17                                    356° C.  6      10    11     12  11                                    ______________________________________                                         *Computer malfunction prevented determination.                           

These results show that the conversion decreases as the temperaturedecreases.

EXAMPLE II

In order to evaluate the effect of elemental magnesium, one gram of the8 percent MoO₃.SiO₂ catalyst was placed in the tubulardisproportionation reactor and calcined at 550° C. for 40 minutes. Thebed was then flushed with nitrogen and 0.03 grams of magnesium added andthe temperature increased to about 660° C. to melt the magnesium. Thattemperature was maintained for about 30 minutes and then the bed cooledto about 350° C. and used to disproportionate the propylene at thattemperature and at a flow rate of about 102 cc/minute.

In another run one gram of the 8 percent MoO₃.SiO₂ catalyst was placedin the tubular reactor and calcined as in the previous run. The calcinedcatalyst was purged with nitrogen and a mixture containing 0.03 gram oftin and 0.09 gram of magnesium was added and then the bed heated to meltthe metals. In contrast to magnesium alone, the combination of metalsmelted at about 550° C. Apparently, the combination of metals results inan alloy of lower melting point. The temperature was maintained at about550° C. for about 30 minutes. Then the bed was cooled to about 353° C.and used in the reaction of propylene. The flow rate was about 104cc/minute.

In yet another run one gram of the 8 percent MoO₃.SiO₂ catalyst wasplaced in the tubular reactor and calcined at about 600° C. for about 30minutes. The bed was then flushed with nitrogen and 0.05 gram of bariumadded. The bed was then heated to 730° C. and maintained at thattemperature for 30 minutes under flowing nitrogen. It was then cooledand used to disproportionate propylene at about 358°-360° C. The flowrate of propylene was about 103 cc/minute.

The results of these three runs are compared with the closest controlrun from Example I in the following Table II.

                  TABLE II                                                        ______________________________________                                        Propylene Conversion, %                                                                            Time                                                     Catalyst    Reaction Temp, °C.                                                                    15    30  45  60  90                               ______________________________________                                        Control     356° C.  6    10  11  12  11                               3% Mg       350° C. 22    22  --  21  19                               3% Sn + 9% Mg                                                                             353° C. 23    25  22  21  20                               5% Ba       358-360° C.                                                                           12    17  19  17  16                               ______________________________________                                    

These results clearly show that elemental magnesium and elemental bariumpromote the MoO₃.SiO₂ catalyst.

What is claimed is:
 1. A composition comprising the product produced bycontacting a refractory oxide containing molybdenum oxide with apromoting amount of a combination of elemental magnesium and elementaltin, said elemental tin being employed in an amount in the range ofabout 1 to about 10 weight percent of the combined weights of saidmolybdenum oxide and said refractory oxide prior to the addition of theelemental metals and said elemental magnesium being employed in anamount in the range of about 0.5 to 20 weight percent of the combinedweights of said molybdenum oxide and said refractory prior to theaddition of the elemental metals.
 2. A composition according to claim 1wherein said refractory oxide is selected from the group consisting ofsilica, alumina and mixtures thereof.
 3. A composition according toclaim 2 wherein said refractory oxide comprises silica.
 4. A compositionaccording to claim 1 wherein said elemental tin is employed in an amountin the range of about 2 to about 5 weight percent of the combinedweights of the refractory molybdenum oxide and the refractory oxideprior to the addition of the elemental metals and said elementalmagnesium is employed in an amount in the range of about 1 to about 10weight percent of the combined weights of the molybdenum oxide and therefractory oxide prior to the addition of the metals.
 5. A compositionaccording to claim 4 wherein said refractory oxide is silica.
 6. Acomposition according to claim 5 wherein said elemental tin is presentin an amount of about 3 weight percent and said elemental magnesium ispresent in an amount of about 9 weight percent of the combined weightsof the molybdenum oxide and the silica prior to the addition of themetals.